Aqueous cleaning composition

ABSTRACT

An aqueous acidic cleaning composition suitable for the cleaning of metal parts is constituted by urea phosphate, a surfactant, a corrosion inhibitor, and water. The corrosion inhibitor can be a phosphatizing compound such as iron phosphate, zinc phosphate, manganese phosphate, and the like.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No.60/672,586 filed on Apr. 19, 2005, incorporated herein by reference.

FIELD OF INVENTION

This invention relates to aqueous cleaning compositions suitable for usein agitation systems.

BACKGROUND OF INVENTION

Agitation systems that employ ultrasonic waves are often utilized inindustrial cleaning operations. In such systems one or more transducersconvert electrical energy to intense, high-frequency vibrations within acleaning bath (ultrasonic cleaning).

Ultrasonic waves generate pressure gradients within a cleaning liquidcontained in the bath and form bubbles within low pressure regions. Theformed bubbles expand until they reach a region of pressure high enoughto collapse the bubbles. As a result, small voids, usually referred toas cavitations continually grow and collapse at the surface of a partthat is submerged in the bath.

The energy created by such cavitations loosens and removes contaminantsthat reside on the surface or surfaces of the part.

The present invention is directed to an aqueous cleaning compositionthat further enhances the efficacy of ultrasonic cleaning of industrialparts.

SUMMARY OF INVENTION

An aqueous cleaning composition which comprises urea phosphate, asurfactant, a corrosion inhibitor, and water is provided. The aqueouscleaning composition is acidic, preferably has a pH value of no higherthan about 2.5, more preferably no higher than about 2.2, and is usefulfor cleaning ferrous as well as non-ferrous metal. If the presentaqueous cleaning solution includes a phosphatizing compound such asferric phosphate, zinc phosphate, manganese phosphate, and the like, thepH value of the composition can be higher, but preferably no higher thanabout 5.5.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The present aqueous cleaning composition is acidic, and is eminentlywell suited for cleaning and deoxidation of metal parts made fromferrous metal such as steel, cast iron, and the like as well as partsmade from aluminum, copper, copper alloys, magnesium, and the like. Thepresent composition can also be used as an activator for iron phosphatecompounds. The pH value of the present compositions usually is in therange of about 2 to about 6, preferably no higher than about 2.5 unlessa phosphatizing agent or phosphatizer is present as a corrosioninhibitor. In such cases the pH value of the composition can be in therange of about 3 to about 6, preferably no higher than about 5.5.

The cleaning composition embodying the present invention is also usefulas a final rinse in an iron phosphate process for steel, galvanizedsteel, aluminum, aluminum alloys, and the like, as well as a final rinseprior to a coating process such as powder coating, spray painting, dipcoating, flow coating, e-coating, and the like.

Urea phosphate salt suitable for present purposes is a reaction productof urea and phosphoric acid (H₃PO₄), and can be represented by theformula

CO(NH₂)₂.H₃PO₄

for urea monophosphate and

CO(NH₂)₂.2H₃PO₄

for urea diphosphate.

Urea-phosphate salts useful for the present purposes can be formed atvarying molar ratios of urea and phosphoric acid. The molar ratio ofurea to phosphoric acid can be in the range of about 1:1 to about 1:5. Amolar ratio of about 1:1 is preferred.

The surfactant component of the present composition is a blend of anon-ionic surfactant and a cationic surfactant capable of removinggrease and oil from the part to be cleaned, preferably a biodegradableblend. Particularly preferred such surfactant is commercially availablefrom Akzo Nobel Surface Chemistry LLC, Chicago, Ill. 60606-9977 underthe designation BEROL® 226 SA.

The corrosion inhibitor suitable for the present purposes preferably isa water-based corrosion inhibitor selected based on the composition ofthe metal parts to be cleaned so as to negate the effects of oxidationand acid/alkali attack. Such corrosion inhibitors include polymericsilicates, triazoles such as benzotriazole, blends of polyamines andthiourea, phosphatizers such as iron (ferric) phosphate, zinc phosphate,manganese phosphate, etc., and the like.

For ferrous metal parts a preferred corrosion inhibitor is a blend ofpolyamines and thiourea, such as the corrosion inhibitor commerciallyavailable from Crown Technology, Inc., Indianapolis, Ind. 46250-0426under the designation CROWN® L 1011 NFNC.

For copper, high copper alloys, aluminum, aluminum alloys, zinc, andzinc alloys a preferred corrosion inhibitor is benzotriazole.

In use, the present aqueous cleaning composition can be further dilutedwith water, if desired. For effective cleaning the concentration of ureais in the range of about 0.1 to about 50 weight percent and theconcentration of phosphoric acid is in the range of about 0.1 to about50 weight percent while maintaining the aforementioned molar ratioranges for urea and phosphoric acid.

A preferred aqueous cleaning composition is constituted by the followingingredients

urea about 43.5 wt.-% phosphoric acid, 85% about 49.8 wt.-% surfactant¹about 0.2 wt.-% corrosion inhibitor² about 0.3 wt.-% water q.s. ¹Berol226 SA, a combination of a non-ionic surfactant (an ethoxylated alcohol)and a cationic surfactant. ²Crown L 1011 NFNC, a blend of polyamines andthiourea.to obtain an aqueous composition having a pH value of about 2.2 andcontaining urea phosphates, i.e., a mixture of urea monophosphate andurea diphosphate.

Optionally, a corrosion inhibitor such as benzotriazole and the like canbe added to the above composition if copper, copper alloy, aluminum, oraluminum alloy parts are to be cleaned. For ferrous metal parts, aphosphatizing compound, e.g., ferric phosphate, zinc phosphate, ormanganese phosphate can be added to the above composition, if desired.This is particularly desirable if the present cleaning solution is to bea final rinse after an iron phosphate treatment.

The foregoing description and the example are intended as illustrative,and are not to be taken as limiting. Variations of the foregoing arepossible without departure from the spirit and scope of the presentinvention and will readily present themselves to those skilled in theart.

1. An acidic aqueous cleaning composition which consists essentially ofa urea phosphate salt, a surfactant, a corrosion inhibitor, and water.2. The composition in accordance with claim 1 wherein the corrosioninhibitor is benzotriazole.
 3. The composition in accordance with claim1 wherein the corrosion inhibitor is a blend of polyamines and thiourea.4. The composition in accordance with claim 1 wherein the urea phosphatesalt is a mixture of urea monophosphate and urea diphosphate.
 5. Thecomposition in accordance with claim 1 wherein pH value of thecomposition is no higher than about 5.5.
 6. The composition inaccordance with claim 1 wherein the composition has a pH value no higherthan about 2.5.
 7. The composition in accordance with claim 1 whereinthe composition has a pH value of about 2.2.
 8. The composition inaccordance with claim 1 wherein the corrosion inhibitor is aphosphatizer.
 9. The composition in accordance with claim 1 wherein thecorrosion inhibitor includes iron phosphate.